The most common operation of an Internet-of-Things (IoT) sensor is short activity bursts separated by long time intervals in sleep or listen modes. During the data bursts, sensed information has to be reliably communicated in real time without draining the energy resources of the sensor node. One way to save such resources is to efficiently code the data burst, use single-channel communication, and adopt ultra-low-power communication circuit techniques.
Typical networks use a single-wire protocol that does not require any Clock and Data Recovery (CDR) circuit. These devices are powered using the charge of a capacitor and their power requirements are quite minimal. The networks using this architecture are called Microlans and have been applied in a variety of sensor applications. The main disadvantage of these one-wire protocols is their very low data rate—limited to 16 Kb/s. It is expected that IoT sensors such as imagers triggered by environmental events (motion, chemical concentrations, temperature, etc.) will require much higher data rates for the transmission of information. Some applications transfer data in standard protocols such as the serial RS232-UART with data rate in the range of few Kb/s.
High-data-rate, single-wire communication can be achieved by encoding/decoding bits onto the cycles of a carrier waveform. To ensure transmission reliability, the carrier signal needs to have a high voltage amplitude (±15 V) thus requiring power conversion and other special circuitry. Line coding techniques, like Non Return to Zero, Manchester, Alternate Mark Inversion, etc., are bit-time dependent and require either a CDR for clock synchronization or a higher clock rate to sample the line to detect edges or to measure the time between edges. Another process is Universal Serial Bus (USB), which achieves high data rates but is known to be very power-hungry due to its complexity and to the need of an external controller to execute all the transfers. In general, digital systems operating at low clock rates (few MHz) and receiving serial data using a one-wire channel operating at a relatively high data rate will need a CDR to receive and recover data without errors. CDR circuits are typically significant consumers of energy on traditional single-channel communication protocols. As such, improved systems and methods for low-power single-wire communication are needed.